The ability to measure chemicals and molecules in human coronary arteries could improve our understanding of plaque formation, plaque progression, the events leading to coronary thrombosis, and the response to pharmacologic therapy.
Optical coherence tomography (OCT), including TD-OCT, OFDI, or SD-OCT can image over large areas of tissue with high spatial resolution, and is sensitive to the morphological features such as macrophages and cap thickness. In one embodiment, OFDI generates axial depth profiles at high spatial resolution by measuring the delay of the source signal as it is reflected by subsurface structures. While OCT techniques has been demonstrated to be capable of visualizing lipid pools, such lipid pools appear as the absence of OCT signal, making them possibly difficult to definitively identify. Furthermore, OCT techniques can be subject to artifacts that give the appearance of lipid pool when one may not be present. A system, apparatus and method for independently determining the presence or absence of lipid can be desirable because of these phenomena. Other components within plaques, including collagen, smooth muscle cells, hemoglobin, thrombus, red blood cells, calcium, etc. can at times pose similar diagnostic challenges. Beyond atherosclerosis, the interpretation of images in other organ systems, such as the GI tract, urinary tract, lung, breast, brain, head and neck can also be challenging as the conventional mode of contrast in OCT is scattering and does not directly provide information on the chemical and molecular composition of the tissue.
While the microstructural information provided by OCT and OFDI techniques is important, the capability to investigate coronary plaques on the chemical and molecular level can be needed to gain a deeper understanding of coronary artery disease. Spectroscopic OCT (SOCT) technique is a post-processing technique that uses time-frequency analysis performed on the interferometric data to generate depth resolved spectra. In tissues, mechanisms that change the spectral content of sample arm light and generate SOCT contrast include changes in scatter size or scatter density, and endogenous or exogenous absorbing agents. Endogenous lipid contrast in coronary OCT is possible when the bandwidth of the OCT light source overlaps at least partially with spectral absorption features of interest. In an exemplary embodiment where spectroscopic OCT is used to characterize atherosclerotic plaques, the common wavelengths used for OCT overlap spectral absorption peaks of lipid within the range of 1250-1350 nm, 1200-1400 nm, or more broadly 1000-1400 nm.
Thus, it may be beneficial to address and/or overcome at least some of the deficiencies of the prior approaches, procedures and/or systems that have been described herein above.